Page 60 - Biology Form Two

Biology for Secondary Schools

Several common disorders and
diseases affect various parts of the
digestive system such as the teeth,
oesophagus, stomach, ileum, and
colon. Examples include dental caries, (a) Enamel caries (b) Dentine caries
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heartburn, indigestion, stomach ulcers,
constipation, and flatulence.

Dental caries
This is usually known as tooth decay.

It occurs when bacteria destroy the (c) Pulp affected (d) Abscess
outer part of the tooth or enamel. Also, Figure 2.9: Development of dental caries
it can occurs through drinking water
with a high fluoride concentration. Symptoms of dental caries
Toothache, especially after eating
(i)
Dental caries develop over time. When sweet, cold, or hot foods.
there are food remains in the mouth, (ii) Gums bleeding, especially during
bacteria present in the mouth combine teeth brushing.

with saliva with food remains to form (iii) Development of holes or cavities
plaque. This is a sticky white substance in the teeth.
often found between teeth. The plaque Prevention and control of dental caries

begins to form within 20 minutes after (i) Brush teeth regularly with
eating food. Bacteria in the plaque recommended toothpaste, at least

convert food remains, especially twice a day to get rid of plaque.
sugar and starch into lactic acid. The (ii) Use dental floss when necessary to
produced acid dissolves the tooth remove the plaque between your

enamel, forming a cavity or a hole in it, teeth.
which exposes the softer inner part or (iii) Wash your mouth after taking
the dentine. If this cavity or hole is not sugary foods like cakes,

treated, it reaches the pulp cavity and chocolates, and biscuits.
nerve endings inside the tooth, causing (iv) Minimise your intake of sugary
an infection and serious pain. Figure foods. This helps to limit the

2.9 shows the development of dental amount of acid produced by
caries. bacteria, hence the minimum risk
of dental decay.

54 Student’s Book - Form Two

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BIOLOGY FORM 2 NEW.indd 54
BIOLOGY FORM 2 NEW.indd 54 05/10/2024 15:36:24